At present, pilot works are being carried out at the fields in Western Siberia to extract oil from the Bazhenov formation. The Bazhenov formation has a complex composition, which contains inorganic substances, as well as organic compounds, such as mobile and sorbed hydrocarbons, kerogen and bitumen. The main inflow was obtained from carbonate-siliceous-clay intervals, the reservoir type is porous-microcavernous and fractured-cavernous. To ensure profitable oil production, wells are put into operation after hydraulic fracturing (HF). However, the dynamics of well production rates is characterized by a high rate of decline, which leads to unprofitable production. An urgent task of developing the Bazhenov formation is to ensure profitable production rates during operation. One of the solutions to this problem is the acid treatment of the bottomhole zone of wells. High reservoir pressure and temperature, low permeability, and complex composition impose a number of restrictions on process fluids and acid compositions for wellworks. The decrease in the filtration properties of the bottomhole zone of wells significantly depends on the impact of process fluids during drilling, development and HF. With the increase in the number of well interventions salt deposits problems come to the fore.
The article presents a design methodology for integrated treatment of the bottomhole zone to restore and maintain well productivity. The methodology includes laboratory testing of core material, sediment samples from wells and process fluids. Based on the results of laboratory studies, it was found that the use of fresh water leads to significant swelling of core samples, the core solubility in acid compositions (hydrochloric acid, clay acid) varies in a wide range (from units to tens of percent). Filtration experiments have shown that the squeezing of process fluids into the reservoir leads to a decrease in filtration properties due to swelling and clogging of the rock. It was found that the treatment composition must be selected for each well individually based on the rock lithotypes in the formation section, the properties of formation fluids and previously used process fluids. The effectiveness of design methodology is confirmed by field tests. The maximum oil production increments were obtained for the designs proposed taking into account the developed recommendations.
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